The Extensible Authentication Protocol (EAP) is a framework for authentication, with many authentication standards derived from it. The EAP protocol is disclosed in “Extensible Authentication Protocol (EAP)”, RFC 3748 (available as free download via the Internet).
Some of the derived standards refer, for example, to:                EAP-SIM as disclosed in “Extensible Authentication Protocol Method for Global System for Mobile Communications (GSM) Subscriber Identity Modules (EAP-SIM)”, RFC 4186.        EAP-AKA as disclosed in “Extensible Authentication Protocol Method for 3rd Generation Authentication and Key Agreement (EAP-AKA), RFC 4187.        EAP-AKA′ as disclosed in “Improved Extensible Authentication Protocol Method for 3rd Generation Authentication and Key Agreement (EAP-AKA′), RFC 5448.        
These standards use credentials on mobile phone's SIM or USIM card to identify, authenticate and obtain authorization on a WLAN. That is, information originally intended for mobile broadband access is used to gain access to another kind of network (WLAN). Other EAP standards use similar key/credential material from other sources.
EAP-based authentication mechanisms often use a backend AAA server to authenticate a user. For example, a WLAN access point (AP) supporting EAP-SIM, EAP-AKA or EAP-AKA′ uses a mobile network operator's AAA server to authenticate WLAN users. Every user provisioned in that AAA server will be granted access to an AP which authenticates against that particular AAA server.
There are many EAP-based authentication mechanisms. Several of them use some a form of credential/identity/key information to authenticate against a WLAN access point, where the actual authentication happens by using some form of AAA server in a backend, and the AP acts as an intermediate instance, running the necessary protocols and protocol conversions.
EAP-SIM/AKA/AKA′ are some of those authentication protocols, using SIM or USIM credentials. They are of particular interest to mobile operators, because they allow using mobile network authentication infrastructure for WLAN authentication. This, in turn, allows a mobile operator to offer WLAN access (“hotspots”) to his mobile subscribers without the need for the mobile subscribers to configure WLAN passwords etc. Since the authentication is based on SIM or USIM credentials, the network operator then has the ability to use his charging infrastructure to charge the user for provided WLAN services.
However, there are different scenarios in which not every user provisioned in that AAA server should be granted access to an AP. By contrast, it should be possible to provide an infrastructure that only a specific user who has obtained a special access right via a third party should be granted access.
Restricting access to WLAN when there is an authentication protocol that authenticates against some backend AAA server would require changing authorizations in that backend server. If that backend server is, however, controlled by a different entity than the entity granting the special access it would require the later to have access to mission-critical infrastructure of the former. That is not desirable.
Several sets of short-range wireless communication technologies exist. Examples of short range communication are Bluetooth and near field communication (NFC). NFC and Bluetooth are both short-range communication technologies that may be integrated into mobile devices (like e.g. smartphones). NFC is supported by different operating systems, like e.g. Android systems. NFC typically requires a distance of 4 cm or less to initiate a connection. NFC allows to share small payloads of data between an NFC tag and an end device, or between two end devices. Tags can range in complexity. Simple tags offer just read and write semantics, sometimes with one-time-programmable areas to make the card read-only (write-once, read-many WORM). More complex tags offer more operations, and have cryptographic hardware to authenticate access to a sector. The most sophisticated tags contain operating environments, allowing complex interactions with code executing on the tag. The data stored in the tag can also be written in a variety of formats. For example for Android systems, many of the Android framework APIs are based around a NFC Forum standard called NDEF (NFC Data Exchange Format).